healthy_workplaces- (1)

8/7/2019 Healthy_workplaces- (1)

1/22

Healthy Workplaces: Plantscaping for Indoor Environmental Quality

Andrew Smith

Research Associate, School of the Built Environment, Liverpool John Moores

University, Byrom Street, Liverpool, L3 3AF, UK

[email protected]

Andrew worked for the Royal Bank of Scotland and in Facilities Management at the

Scottish Parliament before joining the universitys FM research group. His research

focus is on workplace productivity and sustainability.

Michael Pitt

Professor of Facilities Management, School of the Built Environment, Liverpool John

Moores University, Byrom Street, Liverpool, L3 3AF

[email protected]

Michael Pitt is Professor of Facilities Management at Liverpool John MooresUniversity and Visiting Professor in the Faculty of the Built Environment at

Universiti Malaya and is part of the team developing the FM industry in Malaysia. He

is editor of the Journal of Facilities Management and the Journal of Leisure and Retail

Property and joint editor of Urban Design International.


2/22

Abstract

PurposeThe purpose of this paper is to investigate the indoor environmental quality benefits

of plants in offices by undertaking trials using live plants.

Methodology/ApproachUsing two offices in the same building, one with plants and one as a control, daily

tests were undertaken for relative humidity, carbon dioxide, carbon monoxide and

volatile organic compounds (VOCs). Results were analysed to identify any

differences between the office with plants and the one without.

FindingsRelative humidity increased following the introduction of plants and more

significantly following additional hydroculture plants being installed, taking it to

within the recommended range. Carbon dioxide was slightly higher in the plantedoffice for the majority of the trial although there was an overall reduction in both

offices. Carbon monoxide levels reduced with the introduction of plants and again

with the additional plants. VOC levels were consistently lower in the non-planted

office.

Research LimitationsIt would be useful to extend this research in a greater range of buildings and with

more flexible VOC monitoring equipment.

Practical ImplicationsThis paper suggests that plants may provide an effective method of regulating the

indoor environmental conditions within buildings. This can potentially lead to

performance gains for the organisation and a reduction in instances of ill-health

among the workforce.

Originality/ValueThe majority of previous studies have relied on laboratory work and experimental

chambers. This research aims to apply previous findings to a real working

environment to determine whether the air purifying abilities of plants have practical

relevance in the workplace.

Key Words: plants, health, productivity, IAQ, humidity, VOCs

Article Type: Research Paper

1. Introduction

Research linking engagement to job performance has now begun to emerge and, while

further research is required, the published studies suggest a positive correlation


3/22


4/22

Roelofsen (2002) highlights that the two most significant factors influencing

productivity are the thermal environment and air quality but that the way in which

people experience air quality is dependent on the thermal environment. Leaman

(1995) concurs, stating that people who are unhappy with temperature and air quality

are more likely to say this affects their productivity at work. Additionally, he adds

lighting and noise conditions to this list. Wood (2003) also states that improvingindoor air quality is among the most profitable investments building managers can

make as even small improvements in IAQ will directly improve productivity. Further,

he outlines that among workplace performance criteria, the environmental factor,

amenity, i.e. level of comfort afforded by natural daylight, views, air quality, cooling,

heating, lighting and catering facilities is ranked 5 in a scale of one to five in

importance in surveys conducted in offices worldwide.

Wood (2003) also states that reduced productivity is difficult to quantify but various

studies have been carried out, measuring various performance factors and it has been

shown that productivity declines sharply as building-related health complaints rise,

with the average productivity loss in most of these studies being 12%.

The outcomes of a study (Leaman, 1995) in which respondents were surveyed on

questions in eight standard groups (environmental conditions, health symptoms,

satisfaction with amenities, time spent in building, time spent at task, productivity,

perceived control, background data) showed that dissatisfaction is greatest with air

quality, which was also associated with the highest reported productivity loss.

In their survey of managers, Crouch and Nimran (1989) studied performance

facilitating and inhibiting factors in the work environment and found that some factors

of the office environment are more prominent than others as facilitators. Supportive

social interaction accounted for 41% of facilitator responses, followed by physical

conditions and ambient environment at 21%, utilities 10%, information and

communication 18% and workplace experience 11%. They also found that the effects

of physical and ambient conditions, utilities and information and communication are

symmetrical in that they are perceived to facilitate performance when they are

favourable and inhibit performance when they are unfavourable and, while less

prominent individually, when combined they account for 40-50% of all responses

about environmental features influencing performance, suggesting that they are

important considerations.

Another factor that appears to be closely related to productivity is employeesatisfaction. It is often assumed that employees who are more satisfied with the

physical environment are more likely to produce better work outcomes (Lee, 2006)

and this is therefore, an important key performance indicator for organisations. Given

that workplace satisfaction is associated with job satisfaction (Sundstrom et al., 1994;

Wells, 2000; Leather et al., 2003) this appears to be a reasonable assumption.

The study by Lee (2006) found that in general, the results supported the belief that

satisfaction with the physical environment leads to job satisfaction and that there were

large discrepancies between employees perceptions of their current status and their

expectations regarding workplace control, flexibility and workplace adequacy aspects.


5/22

Complaints about indoor air quality tend to come under two headings of discomfort

and illness (Rooley, 1997). Building related illnesses include legionnaires disease,

Pontiac fever, humidifier fever, hypersensitivity pneumonitis, occupational asthma

and allergic rhinitis (Williams, 1998). Many complaints relate to temperature, dry

atmosphere, lack of fresh air and tiredness and although these may be widespread,

they are not regarded as illness (Rooley, 1997). These symptoms may be attributable,in many cases, to Sick Building Syndrome (SBS).

Some symptoms of SBS are considered to be in the illness category according to the

World Health Organisations June 1982 Report (Rooley, 1997) and these include eye,

nose and throat irritation; dry skin; dry mucous membranes; erythema (skin rash);

mental fatigue; headaches; high frequency of airway infections and cough; hoarseness

and wheezing; hyper-sensitivity; nausea and dizziness.

Modern construction methods have seen a move towards cheaper, lower maintenance

and more durable building materials to replace traditional products such as stone and

wood. Modern industry has responded to the market opportunity and contemporarybuildings are now constructed with and contain more manufactured rather than natural

substances, many being petrochemical based. Wood is replaced by UPVC for

windows, synthetic materials replace wool in carpets and plastic replaces wooden

furniture and fittings. The market cost of these products does not reflect their real cost

in terms of externality effects such as environmental impact and their effects on health

(Smith et al., 1998). Additionally, in modern air-conditioned buildings at maximum

heating and cooling load periods, more air is recycled within the building than

exchanged with outside, a factor that may give rise to sick building syndrome (Costa

and James, 1995).

Volatile Organic Compounds (VOCs) are present in buildings, particularly in new or

recently refurbished buildings. They are typically associated with materials derived

from petroleum products and arise in off-gassing from a variety of building products,

furnishings, cleaning products (Williams, 1998), paints, adhesives, carpeting,

upholstery, panelling, plastic, vinyl, copying machines, computers and hundreds of

other office products (Wolverton and Wolverton, 1993). He et al., (2007) found

VOCs to be emitted in varying amounts by the lubricating oil in mechanical parts of

office printers. These include substances such as Benzene and Formaldehyde, which

in low concentrations can cause skin irritation and dry throats but, in higher

concentrations, are linked to cancer.

According to Smith et al., (1998), research in the United States discovered almost

three hundred VOC compounds in a single building and over nine hundred in total.

The commonest VOCs are formaldehyde, organochlorines and phenols and it is now

apparent that these are harmful to health and cause irritation to the skin, eyes, nose

and throat, breathing difficulties, headaches, nosebleeds and nausea, and some are

carcinogens. Additionally, buildings can still contain products related to the burning

of fossil fuels such as carbon monoxide, nitrogen dioxide, sulphur dioxide and carbon

dioxide (Smith et al., 1998).

Guo et al., (2004) carried out a study of indoor environments in Hong Kong to risk

assess exposures to individual VOCs in different environments, including offices.They found that benzene, styrene, methylene chloride, chloroform, trichloroethylene


6/22

and tetrachloroethylene were the most prevalent VOCs in selected indoor

environments.

In the Hong Kong study (Guo et al., 2004), benzene was found to account for

approximately 40% of the lifetime cancer risk associated with each category of indoor

environment. Benzene is a natural component of crude oil (Karakitsios et al., 2007)and is found in a range of office products. It is present in many basic items including

gasoline, inks, oils, paints, plastics and rubber and is used in the manufacture of

detergents, explosives, pharmaceuticals and dyes (Wolverton et al., 1989).

Organochlorines are found in air fresheners, polishes and plastics such as UPVC.

Health effects include eye, skin and lung irritation, headaches, nausea, damage to

central nervous system, depression and they are also carcinogenic and may cause

damage to the liver and kidneys (Smith et al., 1998). Styrene also accounts for a large

proportion of lifetime cancer risk in offices (Guo et al., 2004).

Phenols are found in disinfectants, resins, plastics, paints, varnishes and preservatives.They are corrosive to the skin and can cause damage to the respiratory system (Smith

et al., 1998).

Williams (1998) points out that building occupants may be exposed to many

pollutants simultaneously and although exposure to individual contaminants may be

extremely low, the combined effects over time may be much more significant.

However, sick building syndrome is not caused by VOCs alone. Other factors include

air which is too hot or too dry, biological agents such as carpet mites and pollen, and

particulate matter such as dust and cigarette smoke. Symptoms appear to be worse at

higher temperatures and there is evidence that buildings with air conditioning are

more susceptible than those with natural ventilation (Smith et al., 1998).

Carbon Dioxide is produced by building occupants (Mui, et al., 2008) breathing and

talking. According to Franz (1997), fresh air contains about 21% oxygen and 0.035%

carbon dioxide. However, the oxygen content is reduced to about 17% in air which

has been breathed out, while the carbon dioxide content rises to 4%. The size of the

room, the number of persons occupying it and the ventilating conditions play a

significant role in the dispersal of CO2 (Raza et al., 1991).

Allergen sensitisation occurs when the body is exposed to an allergen resulting in analtered capacity to react to that substance. Further exposure can lead to

immunoreaction such as asthma, rhinitis, alveolitis, dermatitis or eczema (Rooley,

1997). Some allergens found in offices include insect detritus; dust mite excreta and

fungal spores (Penicillium, Trichoderma, Mucro, Cladosporium, Stemphylium,

Aspergillus alternaria) (Rooley, 1997).

Contaminated air may also result from contamination of fresh air intakes such as

emissions from the building itself or other nearby buildings; vehicle exhaust from

street traffic, car parks and loading docks; contamination from industry, streets and

construction sites; or outdoor contaminants from other sources being transferred to

unexpected situations by wind currents (Williams, 1998).


7/22

3. Indoor air quality benefits provided by plants

Air quality benefits provided by indoor plants include improving relative humidity

and reducing volatile organic compounds (VOCs) as well as removing carbon dioxide

from the air and producing oxygen (Smith and Pitt, 2008). The first evidence of the

ability of indoor plants to remove indoor air polluting chemicals was demonstrated inthe early 1980s.

Much of the research into the effects of indoor plants on air quality was carried out in

the United States by Bill Wolverton and his team during research for National

Aeronautics and Space Administration (NASA) into space stations and energy

efficient buildings on earth. The NASA research focused on the ability of plants to

remove pollutants from air and water. NASA researched the issue for over 15 years

(Wolverton et al., 1989).

In the final report of the NASA studies, Wolverton et al., (1989) recommend that

following the first step of reducing the off-gassing from buildings and furnishings

before installation, plants and associated soil microorganisms be used to reduce trace

levels of air pollutants inside future space habitats.

Using a modular structure to represent energy-efficient buildings, Wolverton (1988)

demonstrated a dramatic reduction in air pollution in one side of the structure

containing the plants, while a large number of air pollutants remained in the other side

of the structure, which did not contain plants.

Godish and Guindon (1989) took the NASA research a stage further by examining the

removal capabilities of plants under dynamic conditions, where formaldehyde iscontinuously generated and released from sources with varying emission rates, as

would be the case in residential environments. Formaldehyde was generated and

released within experimental chambers from particle board panels placed within them.

Fully foliated spider plants reduced formaldehyde from initial chamber levels by 29

50% but when the plants were progressively defoliated, formaldehyde levels declined

further, with the greatest formaldehyde reduction (52 90%) occurring when plants

were 50 100% defoliated (Godish and Guindon, 1989). After the plants were

removed from the chambers, the formaldehyde levels slowly recovered to pre-

exposure levels.

Wolverton and Wolverton (1993) conducted experiments with over thirty interior

plants, using plants in potting soil and potting soil without plants to test their ability to

remove formaldehyde, xylene and ammonia from sealed chambers. Similar to the

study by Godish and Guindon (1989), interior panelling made of particle board was

also used as a continuous out-gassing formaldehyde source during their experiments.

The Boston fern (Nephrolepis exaltata Bostoniensis) was found to be the most

effective in removing formaldehyde with a removal rate of 1,863 g per hour,

followed by the pot mum (Chrysanthemum morifolium) at 1,450 g per hour and the

dwarf date palm (Phoenix roebelenii) at 1,385 g per hour. The dwarf date palm was

the most effective at removing xylene with a removal rate of 610 g per hour and the


8/22

lady palm (Rhapis excelsa) was most effective at removing ammonia at 7,356 g per

hour (Wolverton and Wolverton, 1993).

Based on the data obtained by Wolverton and Wolverton (1993), the air in a 9.3

square metre office with a 2.4 metre ceiling would contain 3,916 g of formaldehyde

and 493 g of xylene. Two Boston ferns would be capable of removing theformaldehyde from the air in this office, with approximately three Janet Craigs

(dracaena deremensis) required to remove the same level of formaldehyde. Two

Boston ferns or three Janet Craigs would also be required to remove the xylene from

that office (Wolverton and Wolverton, 1993). The results also indicated that both

leaves and soil microorganisms are involved in removing these chemicals.

Giese et al., (1994) lend support to the idea of room decontamination by plants. In

their study, spider plants were put in contact with formaldehyde over a period of 24

hours and the formaldehyde was removed from the atmosphere of the experimental

glass chamber by the plants within 5 hours to below the detection limit. They suggest

that a single 300g spider plant could detoxify a 100 cubic metre room in six hours.

Oyabu et al., (2003) tested the ability of golden pothos (Epipremmum aureum) to

remove ammonia, formaldehyde and acetone from indoor air. They found the

purification ability to be high for ammonia because it provides nutrition for the plants,

although the ability to remove acetone was much lower, with the acetone level

remaining nearly unchanged. They also found that the purification ability increased

with increasing numbers of pots and that purification takes longer with increasing

molecular weight of the chemical (Oyabu et al., 2003).

The ability of indoor plants to remove carbon dioxide has been well documented.

During photosynthesis, plants absorb carbon dioxide from the atmosphere through the

stomata (tiny openings on the leaves), while the roots absorb moisture from the soil.

Chlorophyll and other tissue in the leaves absorb radiant energy from a light source,

which is used to split water molecules into oxygen and hydrogen. Hydrogen and

carbon dioxide are used by the plant to form sugars, while oxygen, a by-product of

photosynthesis is released into the atmosphere (Wolverton, 1996).

In addition to reducing volatile organic compound concentrations and other gases,

plants may also be used to regulate the indoor climate. Plants such as Rhapis palms

and Marantas, which need regular misting, or plants with high moisture content could

benefit offices with low humidity. It was found that plants can increase the relativehumidity of a non air-conditioned building by about 5%, although the density of

planting required to achieve this was higher than would normally be provided for a

commercial office environment (Costa and James, 1995).

Lohr and Pearson-Mims (1996) found that, during trials of plants impacting on

particulate accumulation, relative humidity was higher when plants were present than

when they were not.

Plants also have the ability to remove airborne particles such as dust or more harmful

particles such as emissions from office printers. Many studies have shown evidence

that outdoor vegetation such as trees and shrubs reduce atmospheric dust but indoorplants also display this characteristic. Plants act as natural filters, causing particles to


9/22

be deposited on the vegetative surface through sedimentation, impaction or

precipitation (Lohr and Pearson-Mims, 1996). Vegetation with rough surfaces from

fine hairs or raised veins for example, is more efficient in reducing airborne

particulates than smooth vegetation (Lohr and Pearson-Mims, 1996).

Their results (Lohr and Pearson-Mims, 1996) showed that in a computer lab,particulate matter was lower in the presence of plants than in their absence. It had

previously been speculated that plants may be a source of particulate matter (Owen et

al., 1992) but these results (Lohr and Pearson-Mims, 1996) showed that plants do not

increase particulate matter but actually reduce it. Particulate matter accumulation was

also substantially lower in the office space when plants were present than when they

were absent, indicating that plants reduce particulates in interior spaces (Lohr and

Pearson-Mims, 1996). Lohr and Pearson-Mims (1996) consider that the accumulation

of particles on horizontal surfaces can be reduced by as much as 20% by adding

foliage plants.

Fjeld (2004) undertook a study where plants were provided in the offices of an oilcompany in Norway and found a 25% reduction in symptoms reported. Instances of

fatigue and headache reduced by 30% and 20% respectively, hoarseness and dry

throat reduced by around 30%, coughing by around 40% and dry facial skin reduced

by about 25%. However, it is unclear whether these results were due to improvements

in air quality made by the plants or psychological factors.

4. Methodology

The trial was carried out in the Edinburgh building of a large financial services

company, located at Edinburgh Park, an out of town business park. The building was

constructed around 15 years ago and the test area comprised two open plan offices on

two floors of the building. These offices were selected due to them being of similar

size and orientation, occupied by approximately the same number of people, doing

similar jobs.

One of these offices was furnished with indoor plants, while the other acted as a

control, with no plants. The office with plants is known as East 1 and the control

office is known as East 2. There was an open atrium between the two offices.

Live interior plants were provided in East 1 for a period of six months from Februaryto the end of July 2008. These were installed and maintained by a professional indoor

landscaping company as previous research has shown that the plants must be in the

optimal condition for them to be successful in regulating the indoor climate within

buildings (Costa and James, 1995; Franz, 1997).

For approximately the first 3.5 months of the trial period, a minimal level of planting

was provided, followed by an increased level of planting for the remainder of the trial

period. The initial installation comprised soil-grown plants and the additional plants

provided later were hydroculture varieties, where the plants are grown in granules and

water is maintained within the plant container. Soil borne pests such as sciarid flies do

not affect hydroculture plants.


10/22

The plants used in the trials were selected for their specific air purification abilities as

well as other factors, such as ease of maintenance, light requirements, size, shape and

general aesthetic qualities.

For the initial period of the trial, the area on East 1 was furnished with two 1.8m Ficus

Alii, one 1.6m branched Dracaena Compacta, two 1.6m Philodendron Scanden, two1.6m Scindapsus Aureum and seven troughs containing screen planting of

approximately 80cm in height. The screen planting comprised of Dracaena Gold

Coast and Calathea Triostar. These represented a minimal level of planting in

comparison to the area of the office. These varieties were all soil-grown plants.

For the second phase of the trial, the level of planting was increased relative to the

area of the office and the plants used were hydroculture varieties. The plants installed

were two 1.05m Schefflera Louisiana, one 1.1m Schefflera Arboricola, two 1.1m

Schefflera Gold Capella, two 80cm Spathiphyllum Sensation, and four troughs, each

containing three 80cm Philodendron Scanden. Additionally, 39 small desk bowls were

provided, each containing one 35 50cm plant from the following varieties: CalatheaOrnata Sanderiana, Calathea Beauty Star, Dracaena Compacta Malaika, Dracaena

Lemon Surprise, Ficus Elastica Melany Petit, Ficus Natasja, Peperomia USA,

Peperomia Red Margin. These plants were selected specifically for their high

transpiration rate, leading to an increased ability to improve indoor relative humidity.

Maintenance of the plants, such as dusting and watering, was carried out on a three-

weekly basis.

Air quality was tested using a Graywolf IAQ-410 air quality monitor on a daily basis.

The monitor was calibrated by a professional independently accredited ISO

9001:2008 and ISO 17025 laboratory in order to ensure the accuracy of the

monitoring equipment. Checks were carried out for humidity, carbon dioxide and

carbon monoxide. Readings were taken at twelve separate locations on each floor and

a daily mean figure calculated for each floor on each day to mitigate the effects of any

erroneous readings due to other factors, for example being closer to a plant or other

item that may affect the reading such as a wet jacket or an open window. Care was

taken to ensure readings were taken at the same locations on each day. Additional

daily checks were completed for total volatile organic compound concentrations,

using a professionally calibrated Tongdy VOC monitor.

Figure 1 shows a floor plan of East 1, detailing the locations of the plants and alsowhere the air quality readings were taken. The layout of East 2 is identical to East 1,

with the exception that the middle circulation area where several meeting tables are

placed in East 1 is an open atrium in East 2. The air quality readings were taken in the

same locations in East 2 as in East 1, except that those in the middle area were taken

close to the railing around the atrium in East 2, whereas in East 1 they were taken in

the middle of the floor.

5. Indoor air quality prior to the trial


11/22

Periodic air hygiene assessments have been carried out within the premises. A

workplace assessment was carried out on 17th

December 2007 and a copy of the

report was provided for the purposes of this research.

Within the report it was noted that airborne particle levels were satisfactory, as were

carbon dioxide, airborne microbes and air temperature. However, relative humiditylevels were recorded below 30%, increasing the risk of health disorders among

sensitive individuals, such as asthma and eczema sufferers, where dry nasal

membranes and skin tissue reduces the protection afforded against sensitising agents.

The recommended range of relative indoor humidity is 40-70%RH. It was noted in the

report that, although change was desirable, there are no humidity controls within the

office areas so no recommendations were made.

6. Results

The expectation was that the presence of plants would increase the humidity level sothat this would be higher in the areas with plants, compared to the control areas

without plants. Additionally, it was expected that humidity levels would increase from

the level recorded before the plants were installed in the test location.

The humidity levels in each area were similar over the period of the trials as is evident

from figure 2, which shows a comparison of the humidity data for each floor for the

period of the trial. However, the trend was for the humidity to be slightly higher on

East 1, where the plants were located, although this is not significant. It is also likely

that the beneficial effects shown on East 1 would have some influence on East 2 as

there is an open atrium, which would enable some air to circulate between each floor,

for example by a stack effect whereby warm air rises within the building. Although

the difference in humidity levels between East 1 and East 2 is not significant, what is

significant is the increase in humidity in East 1, following the introduction of the

plants.

A detailed analysis of humidity levels in East 1 helps to establish the humidity

benefits of plants. Figure 3 shows the daily average humidity and temperature in East

1 from February to August 2008. This is an average of twelve readings taken in each

area of East 1 on each day.

This graph shows that, although there are peaks and troughs, a linear increase inhumidity levels has occurred since the plants were installed in East 1. This has taken

the humidity to within the recommended range of 40-60% RH. Due to the nature of

humidity, peaks and troughs will always exist as a result of the range of factors which

affect it, such as weather conditions, windows being opened or closed, the number of

occupants in the room, flow of people around the room as well as many other factors.

For example, humidity levels will generally be higher if it is raining outside,

particularly as occupants of the building are likely to bring in wet clothes and

umbrellas. However, the aim of the FM department is to bring the humidity level to

generally within the recommended range as far as possible, whereas prior to the

research, it was consistently below 40%RH.


12/22

A further analysis of the data for east 1 is shown in figures 4 and 5. Figure 4 shows

the initial period, where minimal planting was installed and figure 5 shows the latter

period, with an increased number of plants. During the initial period, the humidity

level was shown to rise slightly but it was still below the recommended minimum

level of 40% RH. During the period with increased numbers of plants, the humidity

level rose more steeply to within the recommended range.

The expectation was that the presence of plants would reduce the levels of Carbon

Dioxide and Carbon Monoxide so that the levels of these gases in the areas with

plants would be lower than those of the areas without plants. It was also expected that

carbon dioxide levels recorded prior to the installation of plants would reduce in the

trial area.

Figure 6 shows a comparison of carbon dioxide levels for east 1 and east 2 from

February to August 2008. The data is very close between the two floors and no

significant differences have been identified. Contrary to expectations, the carbon

dioxide level appears to be slightly higher in east 1 for the majority of the trial period.However, carbon dioxide gas is heavier than air so it is likely that some of the carbon

dioxide generated on east 2 would drop to east 1 due to the open atrium.

As with humidity, a more meaningful result is shown when the data for east 1 is

analysed in more detail. Figure 7 shows the daily average figures with minimal plants

installed and figure 8 shows the daily average figures with additional plants installed.

This data shows that the carbon dioxide level reduced significantly with the addition

of plants on east 1 to a level around half that prior to the installation of the plants,

with the exception of an unexplained peak in March, which was consistent across all

readings on a single day, before gradually decreasing again. The reasons for this peak

are unclear and a similar pattern was noted on East 2 on that day. Discussions with the

building management team did not yield any obvious reason for this peak. There was

also not a significant further reduction in carbon dioxide on east 1 with the installation

of additional plants.

Carbon monoxide, although recorded in very small volumes prior to the start of the

trials, was expected to reduce following the installation of the plants. The carbon

monoxide levels reduced relatively significantly from the starting point although

several peaks and troughs were recorded. The downward trend continued with the

addition of more plants in the latter stage of the trials. This data is shown in figure 9.

As plants are known to absorb volatile organic compounds, the expectation was that

VOC levels would be lower in the areas with plants compared to the control areas.

Additionally, it was expected that VOC levels would reduce in the trial areas

compared to the pre-trial levels.

Contrary to this expectation, it was found that VOC levels were consistently lower in

the non-planted area. However, this test was limited by the monitoring equipment,

which required to be plugged in to a mains socket and it did not fit several of the

sockets within the trial building. Therefore, it may be that the locations of some of the

tests were closer to an emitter of VOCs than others.


13/22

Figure 10 shows the comparison of data for east 1 and east 2. A further analysis of the

data for east 1 does show a significant reduction in VOC levels, as shown in figure 11.

The greatest reduction occurred after the installation of additional plants, which

suggests that the VOC level reduced as a result of the installation of plants.

7. Conclusions

This paper details the results of a period of trials of indoor plants in offices, where

indoor air quality was monitored in order to ascertain whether or not the presence of

plants had a beneficial effect on air quality.

The expectation based on previous studies, largely in laboratory settings, was that

following the installation of plants in certain areas, relative humidity would increase,

carbon dioxide and carbon monoxide would reduce and volatile organic compounds

(VOCs) would reduce within these areas.

In the trial building, there was a specific problem with dry indoor air prior to the

commencement of the trial in that humidity was generally lower than the

recommended minimum level. Some staff had been experiencing skin complaints and

other ailments, which were attributed to dry indoor air. The results on humidity were

close between the experimental and control areas but a more detailed analysis of the

results for the experimental area showed that the plants did appear to have a

significant influence, particularly after the installation of additional hydroculture

plants, and the humidity level moved to within the recommended range. It is also

likely that the presence of the plants influenced the air in the control area due to an

open atrium. It would be useful to undertake a further study into the respective

benefits of hydroculture and soil grown plants.

The results on carbon dioxide did not always follow the expected pattern. There was

little difference between the two floors and in fact, the level appeared to be slightly

higher on the floor with the plants for the majority of the trial period. However, as

noted above, there was an open atrium and as carbon dioxide is heavier than air, it is

likely that concentrations would normally be higher in the experimental area because

it was the floor below the control area and, therefore, carbon dioxide generated in the

control area would be likely to drop to the floor below. A further analysis of data from

the experimental group does show a significant reduction of carbon dioxide to around

half its starting value prior to the trial. This suggests that the effect of the plants wassubstantial and influenced the air quality on two floors.Carbon monoxide, although

recorded in small volumes, did decrease relatively significantly, beginning with the

minimal plants and continuing after the addition of more plants.

The results on VOCs did not entirely follow the expected pattern as levels were found

to be consistently lower in the non-planted area. However, further analysis does show

reductions in VOCs following the introduction of the plants, indicating that plants

reduce VOC levels. The slightly lower levels in the areas without plants are

unexplained although this may be due in part to equipment limitations but also to the

open atrium.


14/22

Further research into the VOC content of indoor air is required to establish why the

planted areas generally had higher VOC levels than the non-planted areas. It is known

that plants emit VOCs after wounding but the plants used in the study were

maintained in optimal condition throughout the trial. Therefore, this research needs to

be extended in several buildings to establish whether this is a general trend and to

investigate reasons for it. Another theory that requires investigation is the contributionof the plant containers themselves to VOC emissions. It is inevitable that some VOCs

would be emitted by the plant containers in this study but the actual level is unknown.

It may be possible to define an optimum plant and container package to minimise

VOC emissions.

Overall, these results provide an indication that plants help to balance indoor relative

humidity and reduce carbon monoxide and VOC levels. However, further research

may be useful across a larger sample of buildings to determine whether this pattern of

results can be expected in other buildings, and particularly to establish why the results

on carbon dioxide and VOCs were not more favourable.

In practical terms, plants could prove to be a relatively low maintenance method of

regulating the indoor environmental quality of workplaces.

References

Bakker, A.B., Schaufeli, W.B., Leiter, M.P., Taris, T.W. (2008) Work engagement:

An emerging concept in occupational health psychology. Work & Stress, Vol. 22,

No. 3, pp. 187 200.

Clements-Croome, D., Baizhan,L. (2000) Productivity and indoor environment.

Proceedings of Healthy Buildings 2000, Vol. 1.

Costa, P., James, R.W. (1995) Constructive use of vegetation in office buildings.

Plants for People Symposium, The Hague, Netherlands, 23 November 1995.

Available at:

http://www.healthygreenatwork.org/index_en.cfm?act=artikelen.details&varart=18

[Accessed 30/12/08].

Crouch, A., Nimran, U. (1989) Perceived facilitators and inhibitors of work

performance in an office environment. Environment and Behavior, Vol. 21, No. 2,pp. 206 226.

Fjeld, T. (2004) Do plants in offices promote health? Available from:

http://www.healthygreenatwork.org/index_en_cfm?act=artikelen.details&varart=15

[Accessed: 30/12/2008].

Franz, J. (1997) The Indoor Plants. In Menges, A. (ed.) LOG ID BGW Dresden.

Opus.

Giese, M., Bauer-Doranth, U., Langebartels, C., Sandermann Jr., H. (1994)

Detoxification of formaldehyde by the spiderplant (Chlorophytum comosum L.) and


15/22

by soybean (Glycine max L.) cell-suspension cultures, Plant Physiology, Vol. 104,

pp. 1301 1309.

Godish, T., Guindon, C. (1989) An assessment of botanical air purification as a

formaldehyde mitigation measure under dynamic laboratory chamber conditions,

Environmental Pollution, Vol. 61, pp. 13 - 20.

Guo, H., Lee, S.C., Chan, L.Y., Li, W.M. (2004) Risk assessment of exposure to

volatile organic compounds in different indoor environments, Environmental

Research, Vol. 94, No. 1, pp. 57 - 66.

He, C., Morawska, L., Taplin, L. (2007) Particle emission characteristics of office

printers,Environmental Science and Technology, Vol. 41, No. 17, pp. 6039 6045.

Karakitsios, S.P., Papaloukas, C.L., Kassomenos, P.A., Pilidis, G.A. (2007)

Assessment and prediction of exposure to benzene of filling station employees,

Atmospheric Environment, Vol. 41, No. 40, pp. 9555 9569.

Leaman, A. (1995) Dissatisfaction and office productivity. Facilities, Vol. 13, No.

2, pp. 13 19.

Leather, P., Beale, D., Sullivan, L. (2003) Noise, psychosocial stress and their

interaction in the workplace.Journal of Environmental Psychology, Vol. 23, pp. 213

- 222.

Lee, S.Y. (2006) Expectations of employees toward the workplace and

environmental satisfaction. Facilities, Vol. 24, No. 9/10, pp. 343 353.

Lohr, V.I., Pearson-Mims, C.H. (1996) Particulate matter accumulation on horizontal

surfaces in interiors: Influence of foliage plants. Atmospheric Environment, Vol. 30,

No. 14, pp. 2565 2568.

Mui, K.W., Wong, L.T., Hui, P.S. (2008) Feasibility study on benchmarking indoor

air quality (IAQ) of air-conditioned offices in Hong Kong. Healthy and Creative

Facilities, Proceedings of the CIB W70 Conference in Facilities Management,

Edinburgh, UK, 16th

18th

June 2008, pp. 217 - 223.

Owen, M.K., Ensor, D.S., Sparks, L.E. (1992) Airborne particle sizes and sourcesfound in indoor air.Atmospheric Environment, Vol. 26A, pp. 2149 2162.

Oyabu,T., Sawada, A., Onodera, T., Takenaka, K., Wolverton, B. (2003)

Characteristics of potted plants for removing offensive odors, Sensors and

Actuators B, Vol. 89, pp. 131 136.

Pech, R., Slade, B. (2006) Employee disengagement: Is there evidence of a growing

problem?Handbook of Business Strategy, Vol. 7, No. 1, pp. 21 - 25.

Raza, S.H., Shylaja, G., Murthy, M.S.R., Bhagyalakshmi, O. (1991) The contribution

of plants for CO2 removal from indoor air, Environment International, Vol. 17, pp.343 347.


16/22

Roelofsen, P. (2002) The impact of office environments on employee performance:

the design of the workplace as a strategy for productivity enhancement. Journal of

Facilities Management, Vol. 1, No. 3, pp. 247 - 264.

Rooley, R. (1997), Sick Building Syndrome the real facts: What is known, whatcan be done, Facilities, Vol. 15, No. 1/2, pp. 29 - 33.

Smith, A., Pitt, M. (2009) Sustainable workplaces: Improving staff health and

wellbeing using plants. Journal of Corporate Real Estate, Vol. 11, No. 1, pp. 52 -

63.

Smith, M., Whitelegg, J., Williams, N (1998) Greening the Built Environment.

Earthscan Publications, London.

Sundstrom, E., Town, J.P., Rice, R.W., Osborn, D.P., Brill, M. (1994) Office noise,

satisfaction and performance,Environment and Behavior, Vol. 26, No. 2, pp. 195 -222.

Wells, M. (2000) Office clutter or meaningful personal displays: The role of office

personalization in employee and organizational well-being. Journal of

Environmental Psychology, Vol. 20, No. 3, pp. 239 - 255.

Williams, P. (1998) Air-conditioned environments: System faults affecting occupant

productivity and well-being in Australian buildings, The Cutting Edge 1998. RICS

Research.

Wolverton, B.C. (1988) Foliage plants for improving indoor air quality. National

Aeronautics and Space Administration, Report No. TM-108055. Presented at National

Foliage Foundation Interiorscape Seminar, Hollywood, FL, July 19th

1988. Available

at: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930073015_1993073015.pdf

(Accessed 14/01/2008).

Wolverton, B.C., Johnson, A., Bounds, K. (1989b) Interior landscape plants for

indoor air pollution abatement: Final Report. National Aeronautics and Space

Administration, Report No. TM-101768. Available at:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930073077_1993073077.pdf

(Accessed 14/01/2008).

Wolverton, B.C., Wolverton, J.D. (1993) Plants and soil microorganisms: Removal

of formaldehyde, xylene and ammonia from the indoor environment, Journal of the

Mississippi Academy of Sciences, Vol. 38, No. 2, pp. 11 15.

Wolverton, B.C. (1996)How to grow fresh air: 50 houseplants that purify your home

or office. Weidenfeld and Nicolson, London.

Wood, R.A. (2003) Improving the indoor environment for health, well-being and

productivity. Proceedings of Greening Cities: a new urban ecology, Sydney,

Australia, 30th

April.


17/22

Figure 1: Floor plan of East 1 showing locations of plants and air quality readings

Floor standing plant, 80cm 1.8m (Phase 1 and Phase 2) (Not to scale)

x Location of air quality readingsVOC Location of VOC readings


18/22

Figure 2: Daily Average Humidity: East 1 (with plants) and East 2 (control)

Edinburgh - East 1 v East 2: Daily Average Humidity, February - August 2008

20

25

30

35

40

45

50

55

12/02/2008

19/02/2008

26/02/2008

04/03/2008

11/03/2008

18/03/2008

25/03/2008

01/04/2008

08/04/2008

15/04/2008

22/04/2008

29/04/2008

06/05/2008

13/05/2008

20/05/2008

27/05/2008

03/06/2008

10/06/2008

17/06/2008

24/06/2008

01/07/2008

08/07/2008

15/07/2008

22/07/2008

29/07/2008

05/08/2008

Date

%RH

Humidity Humidity E1

Extra

lantsinstalled

Recommended Min. %RH

Accuracy: +/- 2%RH

Figure 3: Daily Average Humidity East 1 (with plants)

20.0

25.0

30.0

35.0

40.0

45.0

50.0

55.0

12/02/2008

19/02/2008

26/02/2008

04/03/2008

11/03/2008

18/03/2008

25/03/2008

01/04/2008

08/04/2008

15/04/2008

22/04/2008

29/04/2008

06/05/2008

13/05/2008

20/05/2008

27/05/2008

03/06/2008

10/06/2008

17/06/2008

24/06/2008

01/07/2008

08/07/2008

15/07/2008

22/07/2008

29/07/2008

05/08/2008

Date

%RH

Humidity

Extra

lantsinstalled


Accuracy: +/- 2%RH


19/22

Figure 4: Daily Average Humidity East 1 (minimal planting)

20.0

25.0

30.0

35.0

40.0

45.0

50.0

55.0

12/02/2008

19/02/2008

26/02/2008

04/03/2008

11/03/2008

18/03/2008

25/03/2008

01/04/2008

08/04/2008

15/04/2008

22/04/2008

29/04/2008

06/05/2008

Date

%RH

Humidity


Accuracy: +/- 2%RH

Figure 5: Daily Average Humidity East 1 (additional plants)

20.0

25.0

30.0

35.0

40.0

45.0

50.0

55.0

02/06/2008

04/06/2008

06/06/2008

08/06/2008

10/06/2008

12/06/2008

14/06/2008

16/06/2008

18/06/2008

20/06/2008

22/06/2008

24/06/2008

26/06/2008

28/06/2008

30/06/2008

02/07/2008

04/07/2008

06/07/2008

08/07/2008

10/07/2008

12/07/2008

14/07/2008

16/07/2008

18/07/2008

20/07/2008

22/07/2008

24/07/2008

26/07/2008

28/07/2008

30/07/2008

01/08/2008

03/08/2008

05/08/2008

07/08/2008

Date

%RH

Humidity


Accuracy: +/- 2%RH


20/22


21/22

Figure 8: Daily Average Carbon Dioxide: East 1 Additional Planting

400

600

800

1000

1200

02/06/2008

04/06/2008

06/06/2008

08/06/2008

10/06/2008

12/06/2008

14/06/2008

16/06/2008

18/06/2008

20/06/2008

22/06/2008

24/06/2008

26/06/2008

28/06/2008

30/06/2008

02/07/2008

04/07/2008

06/07/2008

08/07/2008

10/07/2008

12/07/2008

14/07/2008

16/07/2008

18/07/2008

20/07/2008

22/07/2008

24/07/2008

26/07/2008

28/07/2008

30/07/2008

01/08/2008

03/08/2008

05/08/2008

07/08/2008

Date

CO2(ppm)

CO2 Linear (CO2)

Recommended Max. CO2 level

Accuracy: +/- 3%

Figure 9: Daily Average Carbon Monoxide: East 1 (with plants) and East 2 (control)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

12/02/2008

19/02/2008

26/02/2008

04/03/2008

11/03/2008

18/03/2008

25/03/2008

01/04/2008

08/04/2008

15/04/2008

22/04/2008

29/04/2008

06/05/2008

13/05/2008

20/05/2008

27/05/2008

03/06/2008

10/06/2008

17/06/2008

24/06/2008

01/07/2008

08/07/2008

15/07/2008

22/07/2008

29/07/2008

05/08/2008

Date

CO(ppm)

CO E2 CO E1

Extraplantsinstalled

Accuracy: +/- 3%


22/22

Figure 10: Daily VOC Levels: East 1 (with plants) and East 2 (control)

20

22

24

26

28

30

32

21/02/2008

28/02/2008

06/03/2008

13/03/2008

20/03/2008

27/03/2008

03/04/2008

10/04/2008

17/04/2008

24/04/2008

01/05/2008

08/05/2008

15/05/2008

22/05/2008

29/05/2008

05/06/2008

12/06/2008

19/06/2008

26/06/2008

03/07/2008

10/07/2008

17/07/2008

24/07/2008

31/07/2008

07/08/2008

14/08/2008

Date

VOC(ppm)

VOC E1 VOC E2

Extra

lantsinstalled

Accuracy: +/- 2%

Figure 11: Daily VOC Levels: East 1 (with plants)

20

22

24

26

28

30

32

21/02/2008

28/02/2008

06/03/2008

13/03/2008

20/03/2008

27/03/2008

03/04/2008

10/04/2008

17/04/2008

24/04/2008

01/05/2008

08/05/2008

15/05/2008

22/05/2008

29/05/2008

05/06/2008

12/06/2008

19/06/2008

26/06/2008

03/07/2008

10/07/2008

17/07/2008

24/07/2008

31/07/2008

07/08/2008

14/08/2008

Date

VOC(ppm)

VOC PPM Linear (VOC PPM)

Extra

lantsinstalled

Accuracy: +/- 2%

healthy_workplaces- (1)

Documents